Lignocellulosic-based composites are formed from small dimension pieces of cellulosic material that are bonded with an adhesive (i.e., a binder). In general, solid wood is fragmented into smaller pieces such as strands, fibers, and chips. An adhesive composition then is added to the wood component. The resulting mixture is subjected to heat and pressure resulting in a composite. The adhesive mix typically is the only non-lignocellulosic component.
The most commonly used wood adhesives are phenol-formaldehyde resins (PF) and urea-formaldehyde resins (UF). There are at least two concerns with PF and UF resins. First, volatile organic compounds (VOC) are generated during the manufacture and use of lignocellulosic-based composites. An increasing concern about the effect of emissive VOC, especially formaldehyde, on human health has prompted a need for more environmentally acceptable adhesives. Second, PF and UF resins are made from petroleum-derived products. The reserves of petroleum are naturally limited. The wood composite industry would greatly benefit from the development of formaldehyde-free adhesives made from renewable natural resources.
Soy protein was used as a wood adhesive for the production of plywood from the 1930's to the 1960's. Petroleum-derived adhesives replaced soy protein adhesives due to the relatively low bonding strength and water resistance of soy protein adhesives. However, soy protein is an inexpensive, abundant, renewable material that is environmentally acceptable.